Aspirated smoke detection (ASD) systems are widely deployed, most commonly, in situations where high sensitivity particle detection is needed to protect valuable systems and infrastructure; and lives. ASD systems typically comprise a particle detector coupled to an air sampling system that delivers an air sample from a location being monitored to the particle detection system. These aspirated smoke detection systems have the dual requirement of high sensitivity and high reliability which present certain engineering challenges.
High sensitivity detection requires that the particle detection system remains accurately calibrated and free from soiling by dust and debris throughout its life. Moreover, it is also preferable that the system has some mechanism to avoid false alarms caused by nuisance and particles which do not indicate the presence of fire. To some extent both ends can be achieved by the use of filters which seek to remove any dust from the sample air so that only smoke particles remain. However, this is not necessarily an easy task as dust particles and smoke particles have size distributions which overlap. Also over time, filters clog and their filtration characteristics may change. This leads to a need to change filters as part of a maintenance schedule. Furthermore the dirtying of the detection chamber of the particle detection system over time as particles settle within the chamber also degrades system performance and impacts reliability. In particular, dirtying of the chamber causes an increase in background radiation within the detection chamber, which effectively adds noise to any detection signal produced and may increase background radiation level to the alarm threshold level in extreme cases.
Accordingly, there is a need for particle detection systems, particularly in the field of aspirating smoke detection systems which better handle the real world situations in which they are used, such that they can maintain detection accuracy, high sensitivity and trouble free operation over long periods.
Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.